A flurry of senior post resignations were reported at the U.S. Department of Defense, a day after President Donald Trump fired Defense Secretary Mark Esper.

According to the Pentagon on Tuesday, James Anderson, acting under secretary of defense for policy; Joseph Kernan, acting under secretary for intelligence and security; and Jen Stewart, chief of staff to the secretary, all submitted letters of resignation. It remains unclear whether the officials voluntarily resigned.

Anderson has been at the Pentagon since 2018, serving first as the assistant secretary for strategy, and later as the deputy under secretary for policy, before taking over the top policy job upon the ouster of John Rood following policy disagreements.

Aside from concerns over national security being undermined, the vacancies are perceived as being filled by Trump loyalists, raising the question of whether the president will call for initiatives he wants to pursue, opposed by the Pentagon, in his final weeks in office.

Some of the replacements have been at the center of past controversies, such as retired Brig. Gen. Anthony Tata, who made numerous Islamophobic comments and claimed former President Barack Obama was a "terrorist leader."